For the production of effect yarns with periodic or aperiodic effects spinning and twisting machines are used with at least two feed devices, of which at least one is controllable. For this the feed cylinder is switchable by means of electromagnetic couplings between two rotational speeds and a stationary condition. The control of the feed devices results as a rule from a program, which is inserted in the machine according to the operational principle in the form of a punched tape, a punched card, or a cam drum.
Punched tape and punched card control have the disadvantage of expensive program generation. If, that is to say, an effect program goes beyond the simple changeover function of two feed device speeds, a new program must as a rule be tested on the machine. It is then very often necessary to correct the program, which with punched tape or punched cards usually leads to the production of a new program carrier.
With the use of cam drums more or less narrow limits are set on the inventiveness of the effect twist, because the program carrier would become too elaborate in peripheral surfaces. Moreover regard must always be had, with such a revolving program, to the fact that the program record is spread over a predetermined peripheral length of the program carrier.
Since in many cases an exact modular repetition of the effect program is not desired on account of possible patterning in the material during the further processing, the expiring program is interrupted. This means that the predetermined switch point of the feed device is shifted within a module. To carry out this interruption two possibilities are already known, namely first the mechanical, the so-called storage swinging and for the other the electrical by way of a timing relay. The mechanical method has it is true the advantage of running in synchronism with the machine, it effects however an exact repetition of the interruption, so that in the end over a greater length an identical module arises.
Interruptions by means of a timing relay have the disadvantage that the interruption level is always of the same magnitude whereas because of its being asynchronous with the machine it is difficult to produce an effect program with the same interruptions on various machines. Mechanical or electromechanical controls moreover are subject to wear and tear on account of their multiplicity of moving parts. With increasing wear and tear however the departure of the effect pattern from the programmed effect pattern also increases.
The problem of the invention is therefore to produce a switching arrangement for programmed control of such effect twisting and spinning machines, which significantly facilitates alteration of the program and makes possible a greater range of variation in the formation of the program.
According to the invention this is achieved in that the pulse period of each timing pulse delivered by the timing device corresponds to a unit length of thread feed and that this unit magnitude is used for the programming of all switching instructions and functions.
Through the fully electronic effect program control in accordance with the invention the production of varieties of effect is set practically no limits any more while the program is easily initiated, suspended and controlled, and any wear and tear with the result of departures from the program is excluded.
Further characteristics of the switching arrangement in accordance with the invention as well as its advantages will appear from the following description.